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Managed C++/CLI - Send email using Microsoft OAuth 2.0 (Modern Authentication) + EWS/Ms Graph API protocol from Office 365 in background service

You can send email using traditional user/password authentication from Office 365 account by EWS/Ms Graph API Protocol.

However Microsoft will disable traditional user authentication in the future, switching to Microsoft OAuth (Modern Authentication) is strongly recommended now.

Installation

Before you can use the following codes, please download EASendMail SMTP Component and install it on your machine at first. Full sample proejcts are included in this installer.

Install from NuGet

You can also install the run-time assembly by NuGet. Run the following command in the NuGet Package Manager Console:

Install-Package EASendMail

Note

If you install it by NuGet, no sample projects are installed, only .NET assembly is installed.

Add reference

To use EASendMail SMTP Component in your project, the first step is Add reference of EASendMail to your project. Please create or open your project with Visual Studio, then go to menu -> Project -> Add Reference -> .NET -> Browse..., and select Installation Path\Lib\net[version]\EASendMail.dll from your disk, click Open -> OK, the reference of EASendMail will be added to your project, and you can start to use it to send email in your project.

add reference in c#/vb.net/c++/cli/clr

.NET assembly

Because EASendMail has separate builds for .Net Framework, please refer to the following table and choose the correct dll.

Separate builds of run-time assembly for .NET Framework 1.1, 2.0, 3.5, 4.0, 4.5, 4.6.1, .NET Core 3.1, .NET 5.0, .NET Standard 2.0 and .NET Compact Framework 2.0, 3.5.

File .NET Framework Version
Lib\net20\EASendMail.dll Built with .NET Framework 2.0
It requires .NET Framework 2.0, 3.5 or later version.
Lib\net40\EASendMail.dll Built with .NET Framework 4.0
It requires .NET Framework 4.0 or later version.
Lib\net45\EASendMail.dll Built with .NET Framework 4.5
It requires .NET Framework 4.5 or later version.
Lib\net461\EASendMail.dll Built with .NET Framework 4.6.1
It requires .NET Framework 4.6.1 or later version.
Lib\netcoreapp3.1\EASendMail.dll Built with .NET Core 3.1
It requires .NET Core 3.1 or later version.
Lib\net5.0\EASendMail.dll Built with .NET 5.0
It requires .NET 5.0 or later version.
Lib\netstandard2.0\EASendMail.dll Built with .NET Standard 2.0
It requires .NET Standard 2.0 or later version.
Lib\net20-cf\EASendMail.dll Built with .NET Compact Framework 2.0
It requires .NET Compact Framework 2.0, 3.5 or later version.
Lib\net35-cf\EASendMail.dll Built with .NET Compact Framework 3.5
It requires .NET Compact Framework 3.5 or later version.

Office 365 OAuth 2.0 client credentials grant

Normal OAuth requires user input user/password for authentication. Obviously, it is not suitable for background service. In this case, You can use the OAuth 2.0 client credentials grant, sometimes called two-legged OAuth, to access web-hosted resources by using the identity of an application. It only works for Office365 user, it doesn’t work for personal Hotmail account.

Create your application in Azure Portal

To use Microsoft/Office365/Live OAuth (Modern Authentication) in your application, you must create a application in Azure Portal.

Important

You can use any Microsoft user to create the application, it doesn’t require application owner is administrator in your Office365 domain. But your Office365 administrator must authorize the application to access user mailbox.

  • Sign in to the Azure portal using either a work or school account or a personal Microsoft account.
  • If your account gives you access to more than one tenant, select your account in the top right corner, and set your portal session to the Azure AD tenant that you want.
  • In the left-hand navigation pane, select the Azure Active Directory service, and then select App registrations -> New registration.
azure portal new app registration

Single tenant and multitenant in account type

When the register an application page appears, enter a meaningful application name and select the account type.

Select which accounts you would like your application to support.

  • If your application only supports the users in your directory or organization, please select Single tenant type;
  • If your application needs to support all users in Office 365 and Microsoft personal account (hotmail.com, outlook.com), please select Multitenant type, and you must verify publisher.

Because we just need to support Offic365 user in our organization, so select Accounts in this organizational directory only (single tenant).

Do not select supporting Microsoft personal account, because there is no way to access Microsoft personal account in background service.

Important

If you don’t verify publisher for multitenant application, your application will not request access token successfully.

API permissions

  • Click API Permission -> Microsoft Graph -> Delegated Permission -> User.Read.
  • Click API Permission -> Microsoft Graph -> Application Permission -> Mail.Send.
  • Click API Permission -> Add a permission -> APIs in my organization uses -> Office 365 Exchange Online -> Application Permission -> Other permission -> full_access_as_app
azure APIs in my organization uses

Here is permissions list:

azure application api permission list

If your current user is not a user in a verified domain or Offic 365, you will not find Office 365 Exchange Online in API list, then you have to add this API permission manually.

  • Select Manifest in the left-hand navigation under Manage.
  • Locate the requiredResourceAccess property in the manifest, and add the following inside the square brackets ([]):
{
  "resourceAppId": "00000002-0000-0ff1-ce00-000000000000",
  "resourceAccess": [
      {
          "id": "dc890d15-9560-4a4c-9b7f-a736ec74ec40",
          "type": "Role"
      }
  ]
}
  • Select Save.
  • Select API permissions under Manage. Confirm that the full_access_as_app permission is listed.

Client Id and client secrets

Now we need to create a client secret for the application, click Certificates and secrets -> client secrets and add a new client secret.

azure application api permission

After client secret is created, store the client secret value to somewhere.

Important

Please store client secret value by yourself, because it is hidden when you view it at next time.

Branding and verify publisher

Now we click Branding, you can edit your company logo, URL and application name. If your application supports multitenant (access user in all Office 365 and Microsoft personal account), you must complete the publisher verification.

It is not difficult, you can have a look at publisher verification. After publisher verification is completed, your branding is like this:

azure application Authentication Overview

Important

You must complete the publisher verification for multitenant application, otherwise, your application will not request access token correctly.

Client id and tenant

Now you can click Overview to find your client id and tenant.

azure application client id and tenant

Enable TLS Strong Encryption Algorithms in .NET 2.0 and .NET 4.0

Because HttpWebRequest is used to get access token from web service. If you’re using legacy .NET framework (.NET 2.0 and .NET 4.0), you need to enable Strong Encryption Algorithms to request access token:

Put the following content to a file named NetStrongEncrypt.reg, right-click this file -> Merge -> Yes. You can also download it from https://www.emailarchitect.net/webapp/download/NetStrongEncrypt.zip.

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\.NETFramework\v2.0.50727]
"SystemDefaultTlsVersions"=dword:00000001
"SchUseStrongCrypto"=dword:00000001

[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\.NETFramework\v2.0.50727]
"SystemDefaultTlsVersions"=dword:00000001
"SchUseStrongCrypto"=dword:00000001

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\.NETFramework\v4.0.30319]
"SystemDefaultTlsVersions"=dword:00000001
"SchUseStrongCrypto"=dword:00000001

[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\.NETFramework\v4.0.30319]
"SystemDefaultTlsVersions"=dword:00000001
"SchUseStrongCrypto"=dword:00000001

Access token expiration

You don’t have to request access token every time. By default, access token expiration time is 3600 seconds, you can use the access token repeatedly before it is expired.

Important

You should create your client id and client secret, do not use the client id from example codes in production environment, it is used for test purpose. If you got "This app isn't verified" information, please click "Advanced" -> Go to ... for test.

Managed C++/CLI - Send email using Microsoft OAuth + EWS from Office 365 account in background service - example

#include "stdafx.h"

using namespace System;
using namespace System::IO;
using namespace System::Net;
using namespace System::Net::Sockets;
using namespace System::Text;
using namespace System::Threading;
using namespace System::Threading::Tasks;
using namespace System::Runtime::InteropServices;
using namespace EASendMail;

static String^ _postString(String^ uri, String^ requestData)
{
    HttpWebRequest^ httpRequest = (HttpWebRequest^)WebRequest::Create(uri);
    httpRequest->Method = "POST";
    httpRequest->ContentType = "application/x-www-form-urlencoded";

    Stream ^requestStream = httpRequest->GetRequestStream();
    auto requestBuffer = Encoding::UTF8->GetBytes(requestData);
    requestStream->Write(requestBuffer, 0, requestBuffer->Length);
    requestStream->Close();

    try
    {
        HttpWebResponse^ httpResponse = (HttpWebResponse^)httpRequest->GetResponse();
        StreamReader^ reader = gcnew StreamReader(httpResponse->GetResponseStream());
        {
            // reads response body
            String^ responseText = reader->ReadToEnd();
            Console::WriteLine(responseText);
            return responseText;
        }
    }
    catch (WebException ^ex)
    {
        if (ex->Status == WebExceptionStatus::ProtocolError)
        {
            auto response = (HttpWebResponse^)ex->Response;
            if (response != nullptr)
            {
                Console::WriteLine("HTTP: " + response->StatusCode.ToString());
                StreamReader ^reader = gcnew StreamReader(response->GetResponseStream());
                {
                    // reads response body
                    String^ responseText = reader->ReadToEnd();
                    Console::WriteLine(responseText);
                }
            }
        }

        throw ex;
    }
}

static void SendMail()
{
    try
    {
        String^ client_id = "8f54719b-4070-41ae-91ad-f48e3c793c5f";
        String^ client_secret = "cbmYyGQjz[d29wL2ArcgoO7HLwJXL/-.";

        // If your application is not created by Office365 administrator,
        // please use Office365 directory tenant id, you should ask Offic365 administrator to send it to you.
        // Office365 administrator can query tenant id in https://portal.azure.com/ - Azure Active Directory.
        String^ tenant = "79a42c6f-5a9a-439b-a2ca-7aa1b0ed9776";

        String^ requestData =
            String::Format("client_id={0}&client_secret={1}&scope=https://outlook.office365.com/.default&grant_type=client_credentials",
                client_id, client_secret);

        String^ tokenUri = String::Format("https://login.microsoftonline.com/{0}/oauth2/v2.0/token", tenant);
        String^ responseText = _postString(tokenUri, requestData);

        OAuthResponseParser^ parser = gcnew OAuthResponseParser();
        parser->Load(responseText);

        String^ officeUser = "user@mydomain.onmicrosoft.com";
        auto server = gcnew SmtpServer("outlook.office365.com");
        server->Protocol = ServerProtocol::ExchangeEWS;
        server->User = officeUser;

        server->Password = parser->AccessToken;
        server->AuthType = SmtpAuthType::XOAUTH2;
        server->ConnectType = SmtpConnectType::ConnectSSLAuto;

        auto mail = gcnew SmtpMail("TryIt");

        mail->From = officeUser;
        mail->To = "support@emailarchitect.net";

        mail->Subject = "Office 365 background service oauth test";
        mail->TextBody = "this is a test, don't reply";

        auto smtp = gcnew SmtpClient();
        smtp->SendMail(server, mail);

        Console::WriteLine("Message delivered!");
    }
    catch (Exception^ ep)
    {
        Console::WriteLine(ep->ToString());
    }
}

Managed C++/CLI - Send email using Microsoft OAuth + Ms Graph API from Office 365 account in background service - example

#include "stdafx.h"

using namespace System;
using namespace System::IO;
using namespace System::Net;
using namespace System::Net::Sockets;
using namespace System::Text;
using namespace System::Threading;
using namespace System::Threading::Tasks;
using namespace System::Runtime::InteropServices;
using namespace EASendMail;

static String^ _postString(String^ uri, String^ requestData)
{
    HttpWebRequest^ httpRequest = (HttpWebRequest^)WebRequest::Create(uri);
    httpRequest->Method = "POST";
    httpRequest->ContentType = "application/x-www-form-urlencoded";

    Stream ^requestStream = httpRequest->GetRequestStream();
    auto requestBuffer = Encoding::UTF8->GetBytes(requestData);
    requestStream->Write(requestBuffer, 0, requestBuffer->Length);
    requestStream->Close();

    try
    {
        HttpWebResponse^ httpResponse = (HttpWebResponse^)httpRequest->GetResponse();
        StreamReader^ reader = gcnew StreamReader(httpResponse->GetResponseStream());
        {
            // reads response body
            String^ responseText = reader->ReadToEnd();
            Console::WriteLine(responseText);
            return responseText;
        }
    }
    catch (WebException ^ex)
    {
        if (ex->Status == WebExceptionStatus::ProtocolError)
        {
            auto response = (HttpWebResponse^)ex->Response;
            if (response != nullptr)
            {
                Console::WriteLine("HTTP: " + response->StatusCode.ToString());
                StreamReader ^reader = gcnew StreamReader(response->GetResponseStream());
                {
                    // reads response body
                    String^ responseText = reader->ReadToEnd();
                    Console::WriteLine(responseText);
                }
            }
        }

        throw ex;
    }
}

static void SendMail()
{
    try
    {
        String^ client_id = "8f54719b-4070-41ae-91ad-f48e3c793c5f";
        String^ client_secret = "cbmYyGQjz[d29wL2ArcgoO7HLwJXL/-.";

        // If your application is not created by Office365 administrator,
        // please use Office365 directory tenant id, you should ask Offic365 administrator to send it to you.
        // Office365 administrator can query tenant id in https://portal.azure.com/ - Azure Active Directory.
        String^ tenant = "79a42c6f-5a9a-439b-a2ca-7aa1b0ed9776";

        String^ requestData =
            String::Format("client_id={0}&client_secret={1}&scope=https://graph.microsoft.com/.default&grant_type=client_credentials",
                client_id, client_secret);

        String^ tokenUri = String::Format("https://login.microsoftonline.com/{0}/oauth2/v2.0/token", tenant);
        String^ responseText = _postString(tokenUri, requestData);

        OAuthResponseParser^ parser = gcnew OAuthResponseParser();
        parser->Load(responseText);

        String^ officeUser = "user@mydomain.onmicrosoft.com";

        // Set Ms Graph API server address and protocol
        auto server = gcnew SmtpServer("graph.microsoft.com");
        server->Protocol = ServerProtocol::MsGraphApi;

        server->User = officeUser;
        server->Password = parser->AccessToken;
        server->AuthType = SmtpAuthType::XOAUTH2;

        server->ConnectType = SmtpConnectType::ConnectSSLAuto;

        auto mail = gcnew SmtpMail("TryIt");

        mail->From = officeUser;
        mail->To = "support@emailarchitect.net";

        mail->Subject = "Office 365 background service oauth test";
        mail->TextBody = "this is a test, don't reply";

        auto smtp = gcnew SmtpClient();
        smtp->SendMail(server, mail);

        Console::WriteLine("Message delivered!");
    }
    catch (Exception^ ep)
    {
        Console::WriteLine(ep->ToString());
    }
}

TLS 1.2 protocol

TLS is the successor of SSL, more and more SMTP servers require TLS 1.2 encryption now.

If your operating system is Windows XP/Vista/Windows 7/Windows 2003/2008/2008 R2/2012/2012 R2, you need to enable TLS 1.2 protocol in your operating system like this:

Enable TLS 1.2 on Windows XP/Vista/7/10/Windows 2008/2008 R2/2012

Appendix

Comments

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See Also